1. Field of Invention
The present invention belongs to technical fields related to a case for containing an electro-optical unit, such as a liquid crystal panel used as a light valve for a projection display apparatus, for example, a liquid crystal projector, a cased electro-optical apparatus composed of a case mounting or containing the electro-optical unit, and a projection display apparatus having a cased electro-optical apparatus.
2. Description of Related Art
In general, when a liquid crystal panel is used as a light valve for a liquid crystal projector, a bare liquid crystal panel is not disposed on the chassis of the liquid crystal projector. Instead, the liquid crystal panel can be mounted or contained in an appropriate case. This cased liquid crystal panel is disposed onto the chassis. Appropriate screw holes are formed on the case so that the cased liquid crystal panel can be easily fixed onto the chassis.
In such a liquid crystal projector, light emitted from a light source is concentrated and projected onto the cased liquid crystal panel. The light can be transmitted through the liquid crystal panel to project an enlarged image on a screen. Since, in general, the liquid crystal projector is expected to project enlarged images, relatively strong light emitted from the light source, such as a metal halide lamp, is used.
For this reason, a temperature increase in the cased liquid crystal panel becomes a problem. If a temperature increase occurs, the temperature of the liquid crystal interposed between a pair of transparent substrates also increases and causes the liquid crystal to degrade. Specifically, when the light from the light source is uneven, the liquid crystal panel becomes partially heated and so-called ‘hot spots’ are generated. For this reason, the transmittance of the liquid crystal becomes uneven, and the image quality of the projected image is degraded.
Known cased liquid crystal panels have the following problems. For example, a liquid crystal projector capable of displaying color images includes a plurality of cased liquid crystal panels for each color, i.e., red, green, and blue. In this case, the three cased liquid crystal panels for each color must not have extremely different properties. More specifically, as described above, a relatively strong light enters the cased liquid crystal panel, and, as a result, the temperature of the cased liquid crystal panel increases. Preferably, the temperature increase for each cased liquid crystal panel should be kept almost the same.
In general, however, this is difficult to achieve. For instance, when a plurality of cased liquid crystal panels are included in a liquid crystal projector, the cased liquid crystal panels might be disposed in different orientations or might be in different environments. An example of the latter is a situation wherein cooled air sent out from a cooling fan also disposed on the liquid crystal projector operates unevenly upon each liquid crystal panel. For example, one of the liquid crystal panels might receive the cooled air and, thus, will be cooled. On the other hand, another liquid crystal panel might not receive the cooled air and, thus, will not be cooled.
In such a situation, the temperature of one of the liquid crystal panels will increase extremely compared to the other liquid crystal panels. Consequently, it becomes necessary to prevent the degradation of a liquid crystal layer and the generation of hot spots in the liquid crystal panel undergoing the extreme temperature increase. Also, it becomes necessary to maintain an ideal equilibrium in the amount of temperature increase of each liquid crystal panel as much as possible. If equilibrium is not maintained, the liquid crystal projector might not operate stably.
In general, the liquid crystal panel receiving blue light experiences a greater temperature increase compared to the liquid crystal panel receiving red or green light. This might also cause a difference in the properties of each liquid crystal panel.